1. Field of the Invention
The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive comprising a bistable latch with bi-level grooves and a spring restraining force.
2. Description of the Prior Art
With disk drives a disk is rotated about a center axis and a head is actuated radially over the disk to write and read data in concentric data tracks. The rotation of the disk forms an air bearing upon which the head xe2x80x9cfliesxe2x80x9d just above the surface of the disk. The head is coupled to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor. When the disk spins down and the air bearing dissipates (e.g., when the disk drive is powered down), the actuator arm is rotated to move the head away from the data area of the disk to prevent damage to the recorded data as well as to the head. A passive latch mechanism is employed to prevent the actuator arm from rotating and moving the head onto the data area of the disk while the disk drive is powered down.
Prior art latch mechanisms include a magnet attached to a crash stop for latching to a metal tang protruding from a coil portion of a head stack assembly. These types of latches require a magnet of sufficient strength to restrain the actuator arm in the latched position when the disk drive is subjected to rotational shocks. However, when the actuator arm is unlatched during normal operation of the disk drive, a high force is needed to detach the tang from the magnet which can cause the actuator arm to vibrate. The vibration in the actuator arm can damage the head due to xe2x80x9chead-slapxe2x80x9d wherein the head physically contacts the surface of the disk or a ramp.
One known technique for reducing damage due to head-slap is to employ a weaker magnet together with an inertial latch. An inertial latch comprises an inertial arm which rotates and xe2x80x9ccatchesxe2x80x9d the actuator arm when the disk drive is subjected to a rotational shock. When the rotational shock subsides, the inertial arm releases the actuator arm and rotates back into a normal position. However, there are drawbacks associated with an inertial latch, namely they are expensive and unreliable depending on the nature of the rotational shock (e.g., magnitude and orientation).
There is, therefore, a need for a more reliable latching mechanism for use in a disk drive with sufficient restraining force to restrain an actuator arm when subjected to rotational shocks while minimizing vibrations and head-slap during a normal unlatch operation.
The present invention may be regarded as a disk drive comprising a disk drive base and a head stack assembly coupled to the disk drive base, the head stack assembly comprising a tang, an actuator arm, and a head coupled to the actuator arm. The disk drive further comprises a bistable latch for latching the actuator arm in a latched position. The bistable latch comprises a latch base supported by the disk drive base, the latch base comprising a first groove and a second groove, wherein a depth of at least part of the first groove is different than a depth of at least part of the second groove. The bistable latch further comprises a latch arm movable with respect to the latch base, the latch arm comprising a contact surface for contacting the tang and a guide member interacting with the first and second grooves for guiding the latch arm through a predetermined trajectory. A spring comprising a first end and a second end is employed by the bistable latch, wherein the first end of the spring is connected to the latch base, and the second end connected to the latch arm. The guide member interacts with the first groove when latching the actuator arm, and the guide member interacts with the second groove when unlatching the actuator arm.
In one embodiment, each of the first and second grooves comprise a first and second end, and the first and second grooves are connected at both the first and second ends. In another embodiment, the first groove comprises a depression, and the guide member of the latch arm interacts with the depression when the actuator arm is in the latched position. In still another embodiment, the disk drive further comprises an actuator for applying a force to the actuator arm to latch and unlatch the actuator arm. The contact surface of the latch arm contacts the tang while the actuator applies the force to the actuator arm. The latch arm further comprises a restraining surface for contacting the tang when the force applied by the actuator is removed. The contact surface and restraining surface are integrally formed, and the contact surface and restraining surface rotate about a pivot in order to place the restraining surface in a position to contact the tang when latching the actuator arm. In yet another embodiment, the disk drive further comprises a ramp for parking the head during a non-operating mode.
The present invention may also be regarded as a disk drive comprising a disk drive base and a head stack assembly coupled to the disk drive base, the head stack assembly comprising a tang, an actuator arm, and a head coupled to the actuator arm. The disk drive further comprises a bistable latch for latching the actuator arm in a latched position. The bistable latch comprises a latch base supported by the disk drive base, the latch base comprising a guide member. The bistable latch further comprises a latch arm movable with respect to the latch base, the latch arm comprising a contact surface for contacting the tang, and a first groove and a second groove for interacting with the guide member of the latch base for guiding the latch arm through a predetermined trajectory, wherein a depth of at least part of the first groove is different than a depth of at least part of the second groove. A spring comprising a first end and a second end is employed by the bistable latch, wherein the first end of the spring is connected to the latch base, and the second end connected to the latch arm. The guide member interacts with the first groove when latching the actuator arm, and the guide member interacts with the second groove when unlatching the actuator arm.